This invention relates to cleaning solutions and in particular to cold-cleaning solutions for optical and electrical conductors, and electrical contacts.
Cold-cleaning solutions are used to clean cables, equipment, and tools in the electrical power industry. Cold-cleaning solutions are also used to clean fiber-optic cables and to remove flux and flux residue from circuit boards. Typically, a cold-cleaning solution is applied to an object by spraying the cold-cleaning solution on the object using an aerosol or other type of propellent, or by wiping the object with a cloth or sponge soaked with the cold-cleaning solution, and then allowing the cold-cleaning solution to evaporate into the surrounding environment.
Since the cold-cleaning solution is allowed to evaporate into the surrounding environment, the cold-cleaning solution should not evaporate so as to produce a flammable vapor or leave behind a flammable liquid. In addition, the cold-cleaning solution should not evaporate too quickly, such that the cold-cleaning solution does not have time to carry contaminants away from the object, or too slowly, such that further processing of the object is unduly delayed. The cold-cleaning solution also should not be hazardous to humans, or to the environment.
In the electric power industry, the requirements are especially rigorous for a cold-cleaning solution for cable splice preparation. A high-voltage power cable typically includes a conductor covered with an inner semi-conductive layer and a primary insulation layer. The semi-conductive layer is thin and is typically composed of a polymer, such as polyethylene. If a splice has to be made in the cable, the semi-conductive layer must first be completely removed from the portions of the conductor to be adjoined. Otherwise, the splice will have a reduced current-carrying capacity and will ultimately fail. The semi-conductive layer is at least partially removed using a cold-cleaning solution.
Splices in high-voltage power cables are often made under unfavorable conditions. Thus, splices are typically made in a quick manner. Accordingly, it is desirable to use a cold-cleaning solution with a high penetrating ability and good solubility characteristics that evaporates quickly and leaves little if any contaminating residue. It is also desirable for the cold-cleaning solution to have a high dielectric strength so that any solution molecules that do get trapped within the splice will not readily ionize and thereby degrade the primary insulation layer. Since the cold-cleaning solution is often used in confined spaces, such as manholes, it is important that the cold-cleaning solution be non-flammable and non-hazardous to humans.
Traditionally, 1,1,1 Trichloroethane (TCA) was used as the cold-cleaning solution for high-voltage power cables because it has a high penetrating ability and good solubility characteristics, especially with regard to polyethylene, and has a high dielectric strength, a good evaporation rate, and is non-flammable. TCA, however, was identified, along with other chloro-fluoro compounds, as depleting the ozone layer and its manufacture in the U.S. after 1996 was banned. Accordingly, other cold-cleaning solutions have been developed to replace TCA. An example of such a replacement cold-cleaning solution is disclosed in U.S. Pat. No. 5,238,504 to Henry, which is hereby incorporated by reference. Henry discloses a cold-cleaning solution for use in the electrical power industry, wherein the cold-cleaning solution comprises a blend of terpene hydrocarbons and aliphatic or cyclic ketones.
Other replacement cold-cleaning solutions include petroleum distillates, fluroethers and certain chlor-fluoro compounds, and glycol ethers and glycol esters. Such replacement cold-cleaning solutions, however, do not possess all of the favorable characteristics of TCA. Some of the replacement cold-cleaning solutions are flammable, some have a low evaporation rate, and some have mediocre solubility characteristics.
Based upon the foregoing, there is a need in the art for an improved cleaning solution, especially for use in the electrical power industry. The present invention is directed to such a cleaning solution.